Loud Whining Noise from Inside the Engine near the Alternator Area


Asked by Nov 02, 2015 at 02:15 PM about the 2004 Toyota 4Runner SR5 4WD

Question type: Maintenance & Repair

The whining noise started 6 months ago and is getting louder.  Took it to a
mechanic who listened with a long screw driver and said it's from the
alternator bearing.  He replaced it, but the noise still there.  The noise
seems to come from inside the engine above the alternator. The noise gets
louder as the engine is rev'ed up.  What could cause such a noise inside
the engine?  Please help.  Thanks.

7 Answers


the alternator drive belt will have tensioners in it, it is the bearings in the tensioners that have gone, the technician should have noticed this on basic inspection, to replace the tensioners is a job you can do yourself and change the belt whilst you are under the hood.

1 people found this helpful.

if it is the tensioners and belt that are worn, chances are the cambelt may need changing (if fitted) a failing cambelt will result in serious damage and you may need a rebuilt motor.


If it were mine.....I would remove the serpentine belt and briefly start the engine to see if the noise is gone (do not run the engine for more than 30 seconds with the belt removed or it may overheat). If the noise remains probably the timing belt tensioner, idler or related part. If the noise disappears when the serpentine belt is removed, one of the accessories the belt drives likely has a bad bearing or other issue.

1 people found this helpful.

Bob, thank you very much for your reply. Very intelligent way of diagnosing the problem. I will pass on your advise to my mechanic. One more question: my 4Runner 4.0 engine has a timing chain, not timing belt. Is the timing chain set up the same way as a timing belt? With tensioner, idler and related parts? Thanks a lot.

1 people found this helpful.

Yes timing chains have rubbing blocks, and hydraulic tensioners. No point in getting worried about a timing chain unless it starts to make noises on start up. Good quality engine oil at the recommended grade, changed at the recommended interval and a quality oil filter will help maximize the life of the timing chain and the rest of the engine.

I have a whine coming from the engine bay on my 2003 Toyota Tacoma. It sounds like a power steering whining noise, but the dealer replaced the power steering pump and the whine returned a few days later. It seems to make this noise when the temperature is below 35 degrees. The truck has 242,000 miles on it. The timing belt was replaced by the dealer at 180,000 miles along with the water pump as it’s not much more money to replace it while it’s torn apart. It’s been doing this since about 200,000 miles. The truck isn’t driven much anymore except in cold temperatures when there is bad weather. The dealer was wrong about the power steering pump and it was a very expensive wrong call. It was $800 to change that. The pump is $500 still in the box. At those prices, I can’t afford many wrong calls. Can anyone help with this issue? I’ve looked online and although there a several similar issues, it doesn’t seem that anyone has discovered the problem. I love the truck. I’ve owned it since new and it has now become family, but I’m not sure how much expense I can handle before even family and I part ways.


Don, you need to start a new thread with your whining problem.

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